Research has been carried out into a number of aspects of the neuroeffector control of rabbit blood vessels, specifically, a) variation in adrenergic characteristics in vessels of different size and from different sites, b) importance of feedback mechanisms in vascular adrenergic neurotransmission, c) evidence for uneven location of alpha-adrenergic receptor in blood vessel wall, d) changes in adrenergic neuromuscular transmission in experimental hypertension, e) development of vascular neuroeffector mechanism in the fetus and f) methodology for semi-micro studies of adrenergic mechanisms in small blood vessels. The one outstanding feature of all these studies was the variation seen in the measured parameters between the different blood vessels. One overall objective of the study is to relate the variation in these different parameters to the variation in functional characteristics of different vessels. Bibliographic references: Bevan, J.A. and Su, C. "Nerve muscle preparations of vascular smooth muscle." Chapter in Methods in Pharmacology, Vol. III, Ed. E.E. Daniel and D.M. Paton, pp. 439-446, Plenum Press, New York, 1975. MeCulloch, M.W., Bevan, J.A. and Su, C. "Effects of Phenoxybenzamine and norepinephrine on transmitter release in the pulmonary artery of the rabbit." Blood Vessels 12:122-133, 1975.